[Collins] Transformers, was 32S-3 wire

[antqradio at sbcglobal.net]

Doctor J's comment about higher then design line voltage made me think a bit out of the box.

I was always under the impression, mistaken or not, that 117 vac was just the geometric mean for the line voltage limits of 110 to 125 vac.  Designers specifying 117 vac instead of the high limit of 125 vac may have inadvertently created a problem for the rest of us.

I would hope that any well designed power transformer would not saturate at 125 vac on the primary and thus operate at higher then ambient temperatures.  Obviously any transformer with primary taps for 115, 120, 125 is in the well designed category.  

That said, if anyone notices that the power transformer is running too hot to touch in any piece of electronic equipment and that transformer does not have primary taps; I would recommend that you install a power resistor in the primary lead to drop a few volts and run the transformer with 115 vac on the primary.  Much easier to do this then to add a bucking transformer, especially when space is at a premium.

The power transformer is, for the most part, the single most expensive component in just about any piece of equipment.  I am sure that cost pressures have resulted in the design of power transformers with too little iron and copper in them so that they are now close to magnetic saturation at present day line voltages.

Much better to prolong transformer life by reducing the internal heat then trying to find a replacement transformer for your favorite receiver.
Jim


________________________________
 From: Dr. Gerald N. Johnson <geraldj at netins.net>
To: collins at mailman.qth.net 
Sent: Monday, August 26, 2013 10:08 AM
Subject: Re: [Collins] 32S-3 wire
 

I'd think 22 is a size or two small for that circuit, though the current in that wire depends on the external connections. Whether the heaters are wired for 6, 12, or 24 volts. There's no current in the wire from the back to the tubes for the 12 and 24 volt connections, only in the 6 volt connection as with the 516F-2.

With modern line voltages a bit higher than when the rig was designed, the voltage at the tube sockets may still be over the rated 6.3 volts and other than the wire running a little warm there will be no harm. Apparent PA tube live might be shorter if the voltage at the PA tubes is under 6.3 because as tubes age, low voltage for the heater reduces cathode emission so that supplying peak currents gets to be more difficult.

You can check for 6.3 at the 6.3 volt jack on the back, taking care to not short it again, if you wired it up. That was probably used for the pilot lamp in the 312B with the wattmeter.

While I was at Collins, pilot line girls building small number products would often trot over to the warehouse and grab teflon insulated wire to use in place of the specified nylon jacketed PVC because while the teflon was a bit harder to strip (but not much with an automatic stripper) they didn't leave behind burnt insulation when they weren't careful enough with a soldering iron.

73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association

On 8/26/2013 8:04 AM, dmurman at verizon.net wrote:
> Thanks Lynn. I had a spool of 22 gauge wire stranded and used that. The original wire I was told was 22 gauge and colors were white/brown/red if I remember correctly. Checked the transmitter on 40 meters and worked flawlessly.
> 
> 
> David
> WA4ECM
> 
> On 08/26/13, kb6oks at juno.com wrote:
> 
> David
> I probably have what you need but, it will be with Teflon insulation, silver plated stranded copper. What is the wire size and color stripes? If I have a match I will send you a few feet.
> Lynn WR7G
> ____________________________________________________________
> 

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